Slashdot Mirror
University of Cape Town Team Breaks World Water Rocketry Record (uct.ac.za)
New submitter Cycliclogic writes: A team of engineers based at the University of Cape Town recently had their record breaking flights of their water powered rocket Ascension III ratified by the Water Rocket Achievement World Record Association. This record is for a single stage rocket power purely on pressurized water. Two launches must be completed within two hours, the record being set at the mean above-ground altitude of the two flights. The record now stands at a whopping 2723 Feet (830m). You can watch videos of the launches here. (Warning: they're loud.)
...only 152.2 km to go.
In all seriousness, I wonder what they could achieve with a multistage version.
Back in the 70s. Bought a 10,000psi stainless cylinder at surplus. Screwed on a fin set, nozzle and burst plate he constructed. Then filled it 80% with water before building a bonfire around it.
They drank beer until the pressure plate popped out at about 8,000 psi.
They were walking around, stomping out fires in the dessert when a group of nice airmen in a Huey invited them to come and talk. They denied everything.
Apparently Russian launch detection satellites saw the flight. He claims they made 10k meters+.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
I just scanned the articles and didn't see what sort of tank pressures these things use.
Also, do I have to use a tank of water? Or can I make my own as I go? One tank of LH2, one of LO2 .....
Have gnu, will travel.
So, I'm super curious to hear what you think pressurized hydrogen or helium would provide that pressurized air would not.
1) Lower mass. Air at STP is 1.2 g/L. Hydrogen is 0.09 g/L. Looking at the contest rules the pressure vessel has to contain 20% water, so most of the volume is gas. A lighter gas lets you either use more pressure while staying under the 1500 gram limit, or have less dead weight for a given bottle/propellant quantity (whichever way you want to look at it).
2) Non-ideal gasses have different compressability. Not my field, so I can't calculate it, but it's significant enough that the rules forbid it for this reason. You have to use air.
Per rule 1, the 1500 gram limit is "dry" meaning not including fuel which would presumably also mean not including the compressed air. It's the compress-ability that really matters here. You could get a lot more energy into compressed hydrogen than compressed air. But it's against the spirit of the competition.
The rules require that the "Pressure vessel and all external parts of the rocket must be constructed from lightweight nonmetallic materials" AFAIK Carbon Fibre is non-metallic.
The videos linked are the same as those used as part of the record submission. The rules state "To prevent "stomp rockets" competitors using bottled air must leave the rocket at full launch pressure for a period of no less then ten (10) minutes prior to launching." .